Desperate troubleshooting what's next? Catless or not

A6 All/ S6 All
#1

Okay here we go.

I’ve been having troubles with my car since april and I would like some advice on what to do next.
My car has random multiple misfires and misfires on cylinders 1 until 8. They never occured on cylinders 9/10. But only during standstill in D or very slow city traffic everything else goes wonderfull.
This all started after a carbon clean. Before that i’ve never had an engine code.

the whole saga can be found in this thread:

So far: all new gaskets, all new spark plugs, new wire connectors , new HPFP’s, all injectors flow tested and good, carbon cleaned, intake manifold opened and checked (all good), new coil packs, new throttle body manifold, replaced a few vacuum lines.

Result: still intermittend random misfires and misfires on cilinders 1-8 :hot_face: :sweat:

So the engine runs realy smooth, closed valves can hold liquid overnight so no leaks there. No oil consumption… So mechanicaly the engine is just spot on.

This leaves me the conclusion that there may be some fault on the exhaust side since intake side is all checked.
Now the next step is an engine drop for the replacement of all O2-sensors (which don’t have any codes at the moment) without any sign that this will solve anything. Btw i don’t have space to the engine drop myself so i have to pay for the labour :unamused:

Or… gut the cats from underneath the car and put in a JHM tuning in the hope that this will solve the misfires (If they are cat related). Like this it would save me an engine drop.
But i fear the car will be obnoxiously loud and will drone on the highway.

Note that the car has had some insulation material comming out of the exhaust side of bank 3/4 which I can’t explain. Is there some kind of insulation wool in the cats? If so is it possible that the car has ‘gutted’ cat 4 (cylinders 9/10) already and now throws codes for the other cylinders?

I realy don’t know what to do since this journey has costed me over 4000 euro’s already and i don’t want to pay for an engine drop and O2 sensor change to stay with a car that still throws codes at me. That would drive me nuts.

The car only has ±78k miles with a replacement engine under warrantee at 20k miles.

What would you do? :see_no_evil:

#2

Have you tried to remove the breather coupler for the PCV valve, and block it with your hand?
Just to get insurance that it’s not the PCV system?

#3

i forgot to mention there is a new pcv valve installed also :speak_no_evil:

“edit” : I think I’ll replace the pcv one more time just to be sure… even tough it’s new the symptoms don’t add up.

#4

Ok so a few issues.

1 you can’t pull out the cats with the motor in the car so no matter what you have to drop the motor for that.

  1. when you get the misfires can tell you alot about what is wrong.

3 check your fuel trims LTFT data and STFT data that will help work along the resolution.

  1. Take a picture of what is coming out of the exhaust pipe the insulation. It might just be from the mufflers.

Get is some of that data and we can help you walk through the solution. and then help give you the next steps.

#5

I just got a call from the workshop.
The car should be fixed :exploding_head: :partying_face:

They drove it 3 days without a fault now. The thing that seems to have fixed it al was a reset of the ecu but not a VCDS reset but realy relearning the ecu’s to factory settings.

After that it didn’t come back, they also changed a litlle valve under the pcv-valve which seem to have something to do with the stationairy pressures what can explain the nature of the missfires.

If someone wants to check the whole saga also read the link in the OP

#6

Congrats. Always feels great to get your car back after a struggle. That first drive is the best. Looking forward to whenever I get to drive my car again. Godspeed and cheers to many more problem-free miles.

#7

haha thanks, after more than six months of troubleshooting it will be bliss yes!!
waiting for the afternoon to pick up the car feels like a kid waiting for santa :slight_smile:

#8

Make sure to get the parts they changed. It would be helpful to know what they changed. So we can all addd that to the list of one more thing to look into.

Please make sure to report back and let us know if this is really fixed or not.